Why are radiation levels at Bikini Island still so high?

Radiation from nuclear weapon tests conducted on Bikini Atoll during the 1940s and 1950s was supposed to have cleared by now, but a new study has found that the island is still uninhabitable due elevated levels of gamma rays produced by elements such as cesium-137.

According to Autumn S. Bordner, a research fellow working on the K1 Project at the Columbia University Center for Nuclear Studies in New York, and her colleagues, recent estimates of the radioactive fallout levels at Bikini Atoll and the Marshall Islands were based on estimates that relied upon data collected decades ago, not recent on-site measurements.

Scientists had predicted that radiation levels would have dropped to between 16 and 24 millrems per year by this time, according to Science News and Phys.org, which would have meant that it would have been safe for people to live near the testing sites. However, Bordner and her colleagues conducted measurements in six different areas, including Bikini Island, and found that the radiation levels exceed safety standards.

“Our findings suggest that there is significant variation in the levels of external gamma radiation on the islands affected by the US nuclear testing program in the Marshall Islands,” they wrote in their paper. “Notably, Bikini Island is found to have radiation levels exceeding the agreement promulgated by the US and [Republic of the Marshall Islands] governments for safe habitation… [which] suggests that Bikini Island… may not be safe for habitation.”

Radiation ‘not terribly dangerous,’ but exceed mandated levels

Bikini Atoll had the highest gamma radiation levels of the sites tested, with a mean reading of 184 millrems per year, according to Popular Science. Three sites on Enewetak Atoll were found to have an average reading of 7.6 millirems per year, while levels of 19.8 mrem/y were measured at a location on Rongelap, which was serious affected by hydrogen bomb tests in the 1950s.

For reference sake, the researchers also collected readings at Majuro Atoll, an island far enough away from the blast zone to serve as a control, and New York’s Central Park. Majuro Atoll was found to have a 9 mrem/y reading, while Central Park measured at 13 mrem/y, they said.

Despite the fact that the numbers were so much higher than the other sites, Phys.org noted that the 184 mrem/y radiation levels detected at Bikini Island is “not considered terribly dangerous” but does exceed the government-mandated minimum-acceptability levels. Bordner’s team also said that additional studies needed to be done to determine what type of exposure people living on the island could be exposed to, such as through food, before re-habitation can commence.

“Without measuring other exposure pathways, we are not able to make a determination as to whether these islands are indeed safe for habitation,” the authors wrote. “There is a population currently living on Enewetak, in some trepidation as to whether or not their environment is safe.”

“In addition, there is currently a large population of displaced Marshallese people who desire to return to Rongelap and Bikini,” they added. “Given these circumstances, it seems imperative that further steps be taken to analyze additional exposure pathways to make a definitive statement as to whether these islands are safe for habitation.”

So why has the radiation apparently lingered so much longer than initial estimates indicated it would? Study co-author and Columbia physicist Emlyn Hughes told Science News that it was likely due to incorrect assumptions about how quickly radioactive materials would wash off of the island.

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Image credit: US Department of Defense

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